The central bank, in a major change, ended all mystery about its plans for interest rates, stating its aim to keep the current near-zero rate through late 2014.

In a historic shift last week, the Federal Reserve removed all mystery about its plans for interest rates, declaring its intent to maintain the current "exceptionally low" target of near zero percent for the key federal-funds rate "at least through late 2014."

The surprising announcement of the extension of this policy—from a previously anticipated end date of mid-2013—came Wednesday after the two-day meeting of the Federal Open Market Committee, which also brought forth new and lower projections for...